The treatment of infected surface or subsurface lesions in patients has typically involved the topical or systemic administration of anti-infective agents to a patient. Antibiotics are one such class of anti-infective agents that are commonly used to treat an infected abscess, lesion, wound, or the like. Unfortunately, an increasingly number of infective agents such as bacteria have become resistant to conventional antibiotic therapy.
Indeed, the increased use of antibiotics by the medical community has led to a commensurate increase in resistant strains of bacteria that do not respond to traditional or even newly developed anti-bacterial agents. Even when new anti-infective agents are developed, these agents are extremely expensive and available only to a limited patient population.
Another problem with conventional anti-infective agents is that some patients are allergic to the very compounds necessary to their treat their infection. For these patients, only few drugs might be available to treat the infection. If the patient is infected with a strain of bacteria that does not respond well to substitute therapies, the patient's life can be in danger.
A separate problem related to conventional treatment of surface or subsurface infections is that the infective agent interferes with the circulation of blood within the infected region. It is sometimes the case that the infective agent causes constriction of the capillaries or other small blood vessels in the infected region which reduces bloodflow. When bloodflow is reduced, a lower level of anti-infective agent can be delivered to the infected region. In addition, the infection can take a much longer time to 10 heal when bloodflow is restricted to the infected area. This increases the total amount of drug that must be administered to the patient, thereby increasing the cost of using such drugs. Topical agents may sometimes be applied over the infected region. However, topical anti-infective agents do not penetrate deep within the skin where a significant portion of the bacteria often reside. Topical treatments of anti-infective agents are often less effective at eliminating infection than systemic administration (i.e., oral administration) of an anti-infective pharmaceutical.
In the 1980's, it was discovered by researchers that the endothelium tissue of the human body produced nitric oxide (NO), and that NO is an endogenous vasodilator, namely, and agent that widens the internal diameter of blood vessels. NO is most commonly known as an environmental pollutant that is produced as a byproduct of combustion. At high concentrations, NO is toxic to humans. At low concentrations, researchers have discovered that inhaled NO can be used to treat various pulmonary diseases in patients. For example, NO has been investigated for the treatment of patients with increased airway resistance as a result of emphysema, chronic bronchitis, asthma, adult respiratory distress syndrome (ARDS), and chronic obstructive pulmonary disease (COPD).
NO has also been investigated for its use as a sterilizing agent. It has been discovered that NO will interfere with or kill the growth of bacteria grown in vitro. PCT International Application No. PCT/CA99/01123 published Jun. 2, 2000 discloses a method and apparatus for the treatment of respiratory infections by NO inhalation. NO has been found to have either an inhibitory and/or a cidal effect on pathogenic cells.
While NO has shown promise with respect to certain medical applications, delivery methods and devices must cope with certain problems inherent with gaseous NO delivery. First, exposure to high concentrations of NO is toxic, especially exposure to NO in concentrations over 1000 ppm. Even lower levels of NO, however, can be harmful if the time of exposure is relatively high. For example, the Occupational Safety and Health Administration (OSHA) has set exposure limits for NO in the workplace at 25 ppm timeweighted averaged for eight (8) hours. It is extremely important that any device or system for delivering NO include features that prevent the leaking of NO into the surrounding environment. If the device is used within a closed space, such as a hospital room or at home, dangerously high levels of NO can build up in a short period of time.
Another problem with the delivery of NO is that NO rapidly oxidizes in the presence of oxygen to form N02, which is highly toxic, even at low levels. If the delivery device contains a leak, unacceptably high levels of N02 can develop. In addition, to the extent that NO oxides to form N021 there is less NO available for the desired therapeutic effect. The rate of oxidation of NO to N02 is dependent on numerous factors, including the concentration of NO, the concentration of 02, and the time available for reaction. Since NO will react with the oxygen in the air to convert to N02, it is desirable to have minimal contact between the NO gas and the outside environment.
Accordingly, there is a need for a device and method for the treatment of surface and subsurface infections by the topical application of NO. The device is preferably leak proof to the largest extent possible to avoid a dangerous build up of NO and N02 concentrations. In addition, the device should deliver NO to the infected region of the patient without allowing the introduction of air that would otherwise react with NO to produce N02. The application of NO to the infected region preferably decreases the time required to heal the infected area by reducing bacterial levels. The device preferably includes a NO and N02 absorber or scrubber that will remove or chemically alter NO and N02 prior to discharge of the air from the delivery device.